Tue·Mar 27, 2018Tuesday·March 27, 2018

1. 01*

   Hard scale uncertainty in collinear factorization: Perspective from $k_t$-factorization

   Benjamin Guiot🇨🇱

   We analyze two consequences of the relationship between collinear factorization and $k_t$-factorization. First, we show that the $k_t$-factorization gives a fundamental justification for the choice of the hard scale $Q^2$ done in the collinear factorization. Second, we show that in the collinear factorization there is an uncertainty on this choice which will not be reduced by higher orders. This uncertainty is absent within the $k_t$-factorization formalism.

   hep-phPRD(2018)·3 citations
2. 02*

   Simultaneous production of D and B mesons

   Rafal Maciula🇵🇱

   We present results of our studies of double-parton scattering (DPS) effects in simultaneous production of heavy flavour mesons (charm and bottom). We discuss production of charm-bottom and bottom-bottom meson-meson pairs in proton-proton collisions at the LHC. The calculation of DPS mechanism is performed within factorized ansatz where each parton scattering is calculated within $k_T$-factorization approach. The hadronization is done with the help of fragmentation functions. For completeness we compare results for double- and single-parton scattering (SPS). The SPS components are also calculated in the $k_T$-factorization with the help of KaTie Monte Carlo generator. As in the case of double charm production also here the DPS dominates over the SPS, especially for small transverse momenta. We present several distributions and integrated cross sections with realistic cuts for simultaneous production of $D^0{B}^{+}$ and $B^{+}{B}^{+}$, suggesting future experimental studies at the LHC.

   hep-phActa Phys.Polon.B(2018)·1 citation
3. 03*

   Five-Particle Phase-Space Integrals in QCD

   O.Gituliar🇩🇪 · V.Magerya🇩🇪 · A.Pikelner🇩🇪

   We present analytical expressions for the 31 five-particle phase-space master integrals in massless QCD as an $ϵ$-series with coefficients being multiple zeta values of weight up to 12. In addition, we provide computer code for the Monte-Carlo integration in higher dimensions, based on the RAMBO algorithm, that has been used to numerically cross-check the obtained results in 4, 6, and 8 dimensions.

   hep-phJHEP(2018)·16 citations
4. 04*

   On the use of running ${\alpha }_s$ in calculations of radiative energy loss of fast partons in a quark-gluon plasma

   B.G. Zakharov🇷🇺

   The incorporation of running ${\alpha }_s$ for the gluon emission vertex in calculations of radiative parton energy loss in a quark-gluon plasma is discussed. It is argued that the virtuality scale for running ${\alpha }_s$ for induced gluon emission is determined by the square of the transverse momentum of the emitted gluon rather than by the square of the invariant mass of the final two-parton state often used in the literature.

   hep-phnucl-thJETP Lett.(2018)·1 citation
5. 05*

   Entanglement in Reggeized Scattering using AdS/CFT

   Yizhuang Liu🇨🇳 · Ismail Zahed🇺🇸

   The eikonalized parton-parton scattering amplitude at large $\sqrt{s}$ and large impact parameter, is dominated by the exchange of a hyperbolic surface in walled AdS. Its analytical continuation yields a worldsheet instanton that is at the origin of the Reggeization of the amplitude and a thermal-like quantum entropy ${\mathcal{S}}_T$. We explicitly construct the entangled density matrix following from the exchanged surface, and show that its von-Neumann entanglement entropy ${\mathcal{S}}_E$ coincides with the thermal-like entropy, i.e. ${\mathcal{S}}_T={\mathcal{S}}_E$. The ratio of the entanglement entropy to the transverse growth of the exchanged surface is similar to the Bekenstein entropy ratio for a black-hole, with a natural definition of saturation and the on-set of chaos in high energy collisions. The largest eigenvalues of the entangled density matrix obey a cascade equation in rapidity, reminiscent of non-linear QCD evolution of wee-dipoles at low-x and weak coupling. We suggest that the largest eigenvalues describe the probability distributions of wee-quanta at low-x and strong coupling that maybe measurable at present and future pp and ep colliders.

   hep-phhep-thnucl-thPRD(2019)·35 citations
6. 06*

   Predictions for the isolated diphoton production through NNLO in QCD and comparison to the 8 TeV ATLAS data

   Bouzid Boussaha🇩🇿 · Farida Iddir🇩🇿 · Lahouari Semlala🇩🇿

   We present cross section predictions for the isolated diphoton production in next-to-next-to-leading order (NNLO) QCD using the computational framework MATRIX. Both the integrated and the differential fiducial cross sections are calculated. We found that the arbitrary setup of the isolation procedure introduces uncertainties with a size comparable to the estimation of the theoretical uncertainties obtained with the customary variation of the factorization and renormalization scales. This fact is taken into account in the final result.

   hep-phAdv.High Energy Phys.(2018)·3 citations
7. 07*

   Invariants and CP violation in the 2HDM

   Odd Magne Ogreid🇳🇴

   We discuss the importance of basis invariants in the general 2HDM and how these relates to masses and couplings. We also present a simple, yet powerful technique to translate parameters of the potential into combinations of masses and couplings of the theory and apply this to CP odd invariants.

   hep-phPoS(2018)·9 citations
8. 08*

   Low energy process $e^{+}{e}^{-}\to K^{+}{K}^{-}$ in the extended Nambu-Jona-Lasinio model

   M. K. Volkov🇷🇺 · K. Nurlan🇷🇺 · A. A. Pivovarov🇷🇺

   In the extended Nambu-Jona-Lasinio model, the process of production of charged kaon pair on colliding electron-positron beams in the energy interval 1 - 1.7 GeV is described. In studying of this process, we take into account the contact terms when the pairs $K^{+}$ $K^{-}$ are generated by an intermediate photon, and processes with intermediate vector mesons $\rho$, $\omega$ and $\varphi$ in the ground and in the first radially excited states. The results obtained here are compared with experimental data recently received in Novosibirsk and in Stanford.

   hep-phPRC(2018)·3 citations
9. 09*

   Interference-assisted resonant detection of axions

   H. B. Tran Tan🇦🇺 · V. V. Flambaum🇦🇺 · I. B. Samsonov🇦🇺 · Y. V. Stadnik🇩🇪 · D. Budker🇩🇪

   Detection schemes for the quantum chromodynamics axions and other axion-like particles in light-shining-through-a-wall (LSW) experiments are based on the conversion of these particles into photons in a magnetic field. An alternative scheme may involve the detection via a resonant atomic or molecular transition induced by resonant axion absorption. The signal obtained in this process is second order in the axion-electron interaction constant but may become first order if we allow interference between the axion-induced transition amplitude and the transition amplitude induced by the electromagnetic radiation that produces the axions.

   hep-phastro-ph.COphysics.atom-phPhys.Dark Univ.(2019)·14 citations
10. 10*

    Study of Twist-2 GTMDs in scalar-diquark model

    Satvir Kaur🇮🇳 · Harleen Dahiya🇮🇳

    We investigate the Generalized Transverse Momentum-dependent Distributions (GTMDs) describing the parton structure of proton using the light-front scalar-diquark model. In particular, we study the Wigner distributions for unpolarized quark in unpolarized, longitudinally-polarized and transversely-polarized proton. We also investigate the twist-2 GTMDs for unpolarized quark $(\Gamma ={\gamma }^{+})$ in scalar-diquark model.

    hep-phFew Body Syst.(2018)·0 citations
11. 11*

    2HDM without FCNC: off the beaten tracks

    Dipankar Das🇮🇳

    We propose an alternative method of constructing two Higgs-doublet models free from scalar mediated FCNC couplings at the tree-level. In a toy scenario, we have presented semi realistic textures for the Yukawa matrices, which can reproduce the approximate flavor structure in the quark sector. Presence of flavor diagonal but nonuniversal Yukawa couplings emerges as a distinguishing feature of such models.

    hep-phEPJC(2018)·7 citations
12. 12*

    Exploring Higgs boson Yukawa interactions with a scalar singlet using Dyson-Schwinger equations

    Tajdar Mufti🇵🇰

    Higgs, being the first discovery of a fundamental scalar field in the standard model (SM), opens the possibility of existence of other scalar or pseudo scalar particles in nature. Though it does not conclusively fulfill the role of inflaton, it does provide motivation for experimental searches involving interactions of scalar (or pseudo scalar) particles as well as implications of such particles' existence from the perspective of theoretical understanding. Yukawa interactions are among the possible interactions. The considered model addresses Yukawa interaction among the Higgs (and Higgs bar) and a real singlet scalar field using Dyson Schwinger equations (DSEs) over a range of bare coupling values relevant to inflation-related physics for several scalar bare masses and cutoff values. The Higgs mass is kept fixed at two values for two different scenarios. It is found that Higgs propagators are tree level dominated while scalar propagators, despite their dependence on parameter region, do not degenerate over the whole parameter space. The interaction vertices show significant deviations from tree level expression for a number of parameters and exhibit two distinct behaviors. Furthermore, the theory does not show any conclusive sign of triviality over the explored parameter space, despite suppressed vertices for some parameters, particularly for small coupling values in a certain region of parameter space.

    hep-ph1 citation
13. 13*

    Accurate nucleon electromagnetic form factors from dispersively improved chiral effective field theory

    J. M. Alarcón🇺🇸 · C. Weiss🇺🇸

    We present a theoretical parametrization of the nucleon electromagnetic form factors (FFs) based on a combination of chiral effective field theory and dispersion analysis. The isovector spectral functions on the two-pion cut are computed using elastic unitarity, chiral pion-nucleon amplitudes, and timelike pion FF data. Higher-mass isovector and isoscalar t-channel states are described by effective poles, whose strength is fixed by sum rules (charges, radii). Excellent agreement with the spacelike proton and neutron FF data is achieved up to Q^2 \sim 1 GeV^2. Our parametrization provides proper analyticity and theoretical uncertainty estimates and can be used for low-Q^2 FF studies and proton radius extraction.

    hep-phhep-latnucl-exPLB(2018)·30 citations
14. 14*

    Higgs Couplings at High Scales

    Dorival Goncalves🇺🇸 · Tao Han🇺🇸 · Satyanarayan Mukhopadhyay🇺🇸

    We study the off-shell production of the Higgs boson at the LHC to probe Higgs physics at higher energy scales utilizing the process $gg\to h^{\ast }\to ZZ$. We focus on the energy scale dependence of the off-shell Higgs propagation, and of the top quark Yukawa coupling, $y_t(Q^2)$. Extending our recent study in arXiv:1710.02149, we first discuss threshold effects in the Higgs propagator due to the existence of new states, such as a gauge singlet scalar portal, and a possible continuum of states in a conformal limit, both of which would be difficult to discover in other traditional searches. We then examine the modification of $y_t(Q^2)$ from its Standard Model (SM) prediction in terms of the renormalization group running of the top Yukawa, which could be significant in the presence of large flat extra-dimensions. Finally, we explore possible strongly coupled new physics in the top-Higgs sector that can lead to the appearance of a non-local $Q^2$-dependent form factor in the effective top-Higgs vertex. We find that considerable deviations compared to the SM prediction in the invariant mass distribution of the $Z$-boson pair can be conceivable, and may be probed at a $2\sigma$-level at the high-luminosity 14 TeV HL-LHC for a new physics scale up to $\mathcal{O}(1\mathrm{TeV})$, and at the upgraded 27 TeV HE-LHC for a scale up to $\mathcal{O}(3\mathrm{TeV})$. For a few favorable scenarios, $5\sigma$-level observation may be possible at the HE-LHC for a scale of about $\mathcal{O}(1\mathrm{TeV})$.

    hep-phhep-exPRD(2018)·32 citations
15. 15*

    Core formation from self-heating dark matter

    Xiaoyong Chu🇦🇹 · Camilo Garcia-Cely🇩🇪

    Cosmological simulations of the $\Lambda$CDM model suggest that the dark matter halos of dwarf galaxies are denser in their center than what observational data of such galaxies imply. In this letter, we propose a novel solution to this problem by invoking a certain class of dark matter self-heating processes. As we will argue, such processes lead to the formation of dark matter cores at late times by considerably reducing the inner mass density of dwarf-sized halos. For deriving concrete results, we focus on semi-annihilating dark matter scenarios and model the inner region of dark matter halos as a gravothermal fluid. An important aspect of this new solution is that the semi-annihilation effects are much more prominent in dwarf-sized halos than in the more massive halos that host galaxies and clusters, even if the corresponding cross sections are the same. Furthermore, the preferred parameter space for solving the small-scale problem suggests a thermal dark matter candidate with a mass below the GeV scale, which can be probed in dark matter direct and indirect detection experiments.

    hep-phastro-ph.HEJCAP(2018)·18 citations
16. 16*

    Dimensional regularization vs methods in fixed dimension with and without ${\gamma }_5$

    A. M. Bruque🇪🇸 · A. L. Cherchiglia🇧🇷 · M. Perez-Victoria🇪🇸

    We study the Lorentz and Dirac algebra, including antisymmetric $ϵ$ tensors and the ${\gamma }_5$ matrix, in implicit gauge-invariant regularization/renormalization methods defined in fixed integer dimensions. They include constrained differential, implicit and four-dimensional renormalization. We find that these fixed-dimension methods face the same difficulties as the different versions of dimensional regularization. We propose a consistent procedure in these methods, similar to the consistent version of regularization by dimensional reduction.

    hep-phhep-thJHEP(2018)·44 citations
17. 17*

    Perturbative moduli stabilisation in type IIB/F-theory framework

    Ignatios Antoniadis🇫🇷 · Yifan Chen🇫🇷 · George K. Leontaris🇬🇷

    We propose a new mechanism of (geometric) moduli stabilisation in type IIB/F-theory four-dimensional compactifications on Calabi-Yau manifolds, in the presence of 7-branes, that does not rely on non-perturbative effects. Complex structure moduli and the axion-dilaton system are stabilised in the standard way, without breaking supersymmetry, using 3-form internal fluxes. Kähler class moduli stabilisation utilises perturbative string loop corrections, together with internal magnetic fields along the D7-branes world-volume leading to Fayet-Iliopoulos D-terms in the effective supergravity action. The main ingredient that makes the stabilisation possible at a de Sitter vacuum is the logarithmic dependence of the string loop corrections in the large two-dimensional transverse volume limit of the 7-branes.

    ↳ hep-thhep-phEPJC(2018)·92 citations
18. 18*

    Non-paraxial relativistic wave packets with orbital angular momentum

    Dmitry Karlovets🇷🇺

    One of the reasons for the tremendous success of a plane-wave approximation in particle physics is that the non-paraxial corrections to such observables as energy, magnetic moment, scattering cross section, and so on are attenuated as ${\lambda }_c^2/{\sigma }_{\perp }^2\ll 1$ where ${\sigma }_{\perp }$ is a beam width and ${\lambda }_c=\hslash /mc$ is a Compton wavelength. This amounts to less than $10^{-14}$ for modern electron accelerators and less than $10^{-6}$ for electron microscopes. Here we show that these corrections are $|\ell |$ times enhanced for vortex particles with high orbital angular momenta $|\ell |\hslash$, which can already be as large as $10^3\hslash$. We put forward the relativistic wave packets, both for vortex bosons and fermions, which transform correctly under the Lorentz boosts, are localized in a 3D space, and represent a non-paraxial generalization of the Laguerre-Gaussian beams. We demonstrate that it is $\sqrt{|\ell |}{\lambda }_c\gg {\lambda }_c$ that defines a paraxial scale for such packets, in contrast to those with a non-singular phase (say, the Airy beams). With current technology, the non-paraxial corrections can reach the relative values of $10^{-3}$, yield a proportional increase of an invariant mass of the electron packet, describe a spin-orbit coupling as well as the quantum coherence phenomena in particle and atomic collisions.

    ↳ quant-phhep-phphysics.optics1 citation
19. 19*

    The $0\nu \beta \beta$-decay nuclear matrix element for light and heavy neutrino mass mechanisms from deformed QRPA cacluations for ${}^{76}$Ge, ${}^{82}$Se, ${}^{130}$Te, ${}^{136}$Xe and ${}^{150}$Nd with isospin restoration

    Dong-Liang Fang🇨🇳 · Amand Faessler🇩🇪 · Fedor Šimkovic🇸🇰

    In this work, with restored isospin symmetry, we evaluated the neutrinoless double beta decay nuclear matrix elements for ${}^{76}$Ge, ${}^{82}$Se, ${}^{130}$Te, ${}^{136}$Xe and ${}^{150}$Nd for both the light and heavy neutrino mass mechanisms using the deformed QRPA approach with realistic forces. We give detailed decompositions of the nuclear matrix elements over different intermediate states and nucleon pairs, and discuss how these decompositions are affected by the model space truncations. Compared to the spherical calculations, our results show reductions from $30\%$ to about $60\%$ of the nuclear matrix elements for the calculated isotopes mainly due to the presence of BCS overlap factor between the initial and final ground states. The comparison between different nucleon-nucleon forces with corresponding Short-Range-Correlations (src) shows, that the choice of the NN force gives roughly $20\%$ deviations for light exchange neutrino mechanism and much larger deviations for the heavy neutrino exchange mechanism.

    ↳ nucl-thhep-phPRC(2018)·119 citations
20. 20*

    Tetrads in solids: from elasticity theory to topological quantum Hall systems and Weyl fermions

    J. Nissinen🇫🇮 · G.E. Volovik🇫🇮

    Theory of elasticity in topological insulators has many common features with relativistic quantum fields interacting with gravitational field in the tetrad form. Here we discuss several issues in the effective topological (pseudo)electromagnetic response in three-dimensional weak crystalline topological insulators with no time-reversal symmetry that feature elasticity tetrads, including a mixed "axial-gravitational" anomaly. This response has some resemblance to "quasitopological" terms proposed for massless Weyl quasiparticles with separate, emergent fermion tetrads. As an example, we discuss the chiral/axial anomaly in superfluid 3He-A. We demonstrate the principal difference between the elasticity tetrads and the Weyl fermion tetrads in the construction of the topological terms in the action. In particular, the topological action expressed in terms of the elasticity tetrads, cannot be expressed in terms of the Weyl fermion tetrads since in this case the gauge invariance is lost.

    ↳ cond-mat.str-elgr-qchep-phJ.Exp.Theor.Phys.(2018)·36 citations
21. 21*

    Updated constraints on $f(T)$ models using direct and indirect measurements of the Hubble parameter

    S. Basilakos🇬🇷 · S. Nesseris🇪🇸 · F. K. Anagnostopoulos🇬🇷 · E. N. Saridakis🇬🇷

    We extract observational constraints on $f(T)$ gravity, using the recently proposed statistical method which is not affected by the value of $H_0$ and thus it bypasses the problem of the disagreement in its exact numerical value between Planck and direct measurements. We use direct measurements of the Hubble parameter with the corresponding covariance matrix, and for completeness we perform a joint analysis using the latest data from Supernovae type Ia based on JLA sample, quasi-stellar objects, and Cosmic Microwave Background shift parameter from Planck. We analyze a large family of $f(T)$ models, and we compare the fitting results with $\Lambda$CDM cosmology using the AIC statistical test. Utilizing only the Hubble parameter data we find that in the case of the power-law $f(T)$ model a small but non-zero deviation from $\Lambda$CDM cosmology is slightly favored at 1-$\sigma$, nevertheless the corresponding AIC value shows a statistical equivalence with it. Finally, the join analysis reveals that all $f(T)$ models are very efficient and in very good agreement with observations.

    ↳ astro-ph.COhep-phhep-thJCAP(2018)·67 citations
22. 22*

    21cm Limits on Decaying Dark Matter and Primordial Black Holes

    Steven Clark🇺🇸 · Bhaskar Dutta🇺🇸 · Yu Gao🇨🇳 · Yin-Zhe Ma🇿🇦 · Louis E. Strigari🇺🇸

    Recently the Experiment to Detect the Global Epoch of Reionization Signature (EDGES) reported the detection of a 21cm absorption signal stronger than astrophysical expectations. In this paper we study the impact of radiation from dark matter (DM) decay and primordial black holes (PBH) on the 21cm radiation temperature in the reionization epoch, and impose a constraint on the decaying dark matter and PBH energy injection in the intergalactic medium, which can heat up neutral hydrogen gas and weaken the 21cm absorption signal. We consider decay channels DM$\to e^{+}{e}^{-},\gamma \gamma$, ${\mu }^{+}{\mu }^{-}$, $b\bar{b}$ and the $10^{15-17}$g mass range for primordial black holes, and require the heating of the neutral hydrogen does not negate the 21cm absorption signal. For $e^{+}{e}^{-}$, $\gamma \gamma$ final states and PBH cases we find strong 21cm bounds that can be more stringent than the current extragalactic diffuse photon bounds. For the DM$\to e^{+}{e}^{-}$ channel, the lifetime bound is ${\tau }_{\mathrm{DM}}>10^{27}$s for sub-GeV dark matter. The bound is ${\tau }_{\mathrm{DM}}\ge 10^{26}$s for sub-GeV DM$\to \gamma \gamma$ channel and reaches $10^{27}$s at MeV DM mass. For $b\bar{b}$ and ${\mu }^{+}{\mu }^{-}$ cases, the 21 cm constraint is better than all the existing constraints for $m_{\mathrm{DM}}<20$ GeV where the bound on ${\tau }_{\mathrm{DM}}\ge 10^{26}$s. For both DM decay and primordial black hole cases, the 21cm bounds significantly improve over the CMB damping limits from Planck data.

    ↳ astro-ph.HEhep-phPRD(2018)·196 citations
23. 23*

    Asymptotic Bessel-function expansions for Legendre and Jacobi functions

    Loyal Durand🇺🇸

    We present new asymptotic series for the Legendre and Jacobi functions of the first and second kinds in terms of Bessel functions with appropriate arguments. The results are useful in the context of scattering problems, improve on known limiting results, and allow the calculation of corrections to the leading Bessel-function approximations for these functions. Our derivations of these series are based on Barnes-type representations of the Legendre, Jacobi, and Bessel functions; our method appears to be new. We use the results, finally, to obtain asymptotic Bessel function expansions for the rotation functions needed to describe the scattering of particles with spin.

    ↳ math-phhep-phmath.MPJ.Math.Phys.(2019)·1 citation
24. 24*

    The impact of EDGES 21-cm data on dark matter interactions

    Kingman Cheung🇹🇼 · Jui-Lin Kuo🇹🇼 · Kin-Wang Ng🇹🇼 · Yue-Lin Sming Tsai🇹🇼

    The recently announced results on the 21-cm absorption spectrum by the EDGES experiment can place very stringent limits on dark matter annihilation cross-sections. We properly take into account the heating energy released from dark matter annihilation from the radiation epoch to the 21-cm observation redshifts in the radiative transfer to compute the evolution of the gas temperature. Our results show that the global 21-cm absorption profile is a powerful cosmological probe of the dark matter interactions. For dark matter annihilating into electron-positron pairs, the EDGES results give a more stringent upper limit than the PLANCK result on the annihilation cross section at the lower dark matter mass region.

    ↳ astro-ph.COastro-ph.HEhep-phPLB(2019)·74 citations
25. 25*

    Some hadronic parameters of charmonia in ${\mathbf{N}}_{\text{f}}=2$ lattice QCD

    Gabriela Bailas🇫🇷 · Benoît Blossier🇫🇷 · Vincent Morénas🇫🇷

    The phenomenology of leptonic decays of quarkonia holds many interesting features: for instance, it can establish constraints on scenarios beyond the Standard Model with the Higgs sector enriched by a light CP-odd state. In the following paper, we report on a two-flavor lattice QCD study of the ${\eta }_c$ and $J/\psi$ decay constants, $f_{{\eta }_c}$ and $f_{J\psi }$. We also examine some properties of the first radial excitation ${\eta }_c(2S)$ and $\psi (2S)$.

    ↳ hep-lathep-phEPJC(2018)·16 citations
26. 26*

    Are small radii of compact stars ruled out by GW170817/AT2017gfo?

    G. F. Burgio🇮🇹 · A. Drago🇮🇹 · G. Pagliara🇮🇹 · H.-J. Schulze🇮🇹 · J.-B. Wei🇮🇹

    The detection of GW170817 and its electromagnetic counterparts allows to constrain the equation of state of dense matter in new and complementary ways. Very stiff equations of state are ruled out by the upper limit on the average tidal deformability, $\tilde{\Lambda }\lesssim 800$, imposed by the detected gravitational wave signal. A lower limit, $\tilde{\Lambda }\gtrsim 400$, can also be extracted by considering the large amount of ejected matter which powers the kilonova AT2017gfo. By using several microscopic nucleonic equations of state, we first confirm the existence of a monotonic relation between $R_{1.5}$ (the radius of the $1.5M_{\odot }$ configuration) and $\tilde{\Lambda }$. This translates the limits on $\tilde{\Lambda }$ into limits on the radius: $11.8\text{km}\lesssim R_{1.5}\lesssim 13.1$km. We then show that the monotonic relation is violated, if a second branch of compact stars composed of quark matter exists, as in the two-families or the twin-stars scenarios. In particular, it is possible to fulfill the limits on $\tilde{\Lambda }$ while having $R_{1.5}$ significantly smaller than $12$km. In both those scenarios the event GW170817/AT2017gfo originates from the merger of a hadronic star and a star containing quark matter.

    ↳ astro-ph.HEhep-phnucl-thApJ(2018)·129 citations
27. 27*

    Constraining Primordial Black Holes with the EDGES 21-cm Absorption Signal

    Andi Hektor🇪🇪 · Gert Hütsi🇪🇪 · Luca Marzola🇪🇪 · Martti Raidal🇪🇪 · Ville Vaskonen🇪🇪 · Hardi Veermäe🇪🇪

    The EDGES experiment has recently measured an anomalous global 21-cm spectrum due to hydrogen absorptions at redshifts of about $z\sim 17$. Model independently, the unusually low temperature of baryons probed by this observable sets strong constraints on any physical process that transfers energy into the baryonic environment at such redshifts. Here we make use of the 21-cm spectrum to derive bounds on the energy injection due to a possible population of $\mathcal{O}(1-100)M_{\odot }$ primordial black holes, which induce a wide spectrum of radiation during the accretion of the surrounding gas. After calculating the total radiative intensity of a primordial black hole population, we estimate the amount of heat and ionisations produced in the baryonic gas and compute the resulting thermal history of the Universe with a modified version of RECFAST code. Finally, by imposing that the temperature of the gas at $z\sim 17$ does not exceed the indications of EDGES, we constrain the possible abundance of primordial black holes. Depending on uncertainties related to the accretion model, we find that $\mathcal{O}(10)M_{\odot }$ primordial black holes can only contribute to a fraction $f_{\mathrm{PBH}}<(1-10^{-3})$ of the total dark matter abundance.

    ↳ astro-ph.COhep-phPRD(2018)·133 citations
28. 28*

    Lessons from HAWC PWNe observations: the diffusion constant is not a constant; Pulsars remain the likeliest sources of the anomalous positron fraction; Cosmic rays are trapped for long periods of time in pockets of inefficient diffusion

    Stefano Profumo🇺🇸 · Javier Reynoso-Cordova🇲🇽 · Nicholas Kaaz🇺🇸 · Maya Silverman🇺🇸

    Recent TeV observations of nearby pulsars with the HAWC telescope have been interpreted as evidence that the diffusion of high-energy electrons and positrons within pulsar wind nebulae is highly inefficient compared to the rest of the interstellar medium. If the diffusion coefficient well outside the nebula is close to the value inferred for the region inside the nebula, high-energy electrons and positrons produced by the two observed pulsars could not contribute significantly to the local measured cosmic-ray flux. The HAWC Collaboration thus concluded that, under the assumption of isotropic and homogeneous diffusion, the two pulsars are ruled out as sources of the anomalous high-energy positron flux. Here, we argue that since the diffusion coefficient is likely not spatially homogeneous, the assumption leading to this conclusion is flawed. We solve the diffusion equation with a radially dependent diffusion coefficient, and show that the pulsars observed by HAWC produce potentially perfect matches to the observed high-energy positron fluxes. We also study the implications of inefficient diffusion within pulsar wind nebulae on Galactic scales, and show that cosmic rays are likely to have very long residence times in regions of inefficient diffusion. We describe how this prediction can be tested with studies of the diffuse Galactic emission.

    ↳ astro-ph.HEastro-ph.GAhep-phPRD(2018)·113 citations
29. 29*

    Early-Universe Constraints on Dark Matter-Baryon Scattering and their Implications for a Global 21cm Signal

    Tracy R. Slatyer🇺🇸 · Chih-Liang Wu🇺🇸

    We present and compare several cosmological constraints on the cross section for elastic scattering between dark matter (DM) and baryons, for cross sections with a range of power-law dependences on the DM-baryon relative velocity $v$, especially focusing on the case of $\sigma \propto v^{-4}$. We study constraints spanning a wide range of epochs in cosmological history, from pre-recombination distortions to the blackbody spectrum and anisotropies of the cosmic microwave background (CMB), to modifications to the intergalactic medium temperature and the resulting 21cm signal, and discuss the allowed signals in the latter channels given the constraints from the former. We improve previous constraints on DM-baryon scattering from the CMB anisotropies, demonstrate via principal component analysis that the effect on the CMB can be written as a simple function of DM mass, and map out the redshifts dominating this signal. We show that given high-redshift constraints on DM-baryon scattering, a $v^{-4}$ scaling of the cross section for light DM would be sufficient to explain the deep 21cm absorption trough recently claimed by the EDGES experiment, if 100% of the DM scatters with baryons. For millicharged DM models proposed to explain the observation, where only a small fraction of the DM interacts, we estimate that a PIXIE-like future experiment measuring CMB spectral distortion could test the relevant parameter space.

    ↳ astro-ph.COhep-phPRD(2018)·241 citations
30. 30*

    Too Hot, Too Cold or Just Right? Implications of a 21-cm Signal for Dark Matter Annihilation and Decay

    Hongwan Liu🇺🇸 · Tracy R. Slatyer🇺🇸

    Measurements of the temperature of the baryons at the end of the cosmic dark ages can potentially set very precise constraints on energy injection from exotic sources, such as annihilation or decay of the dark matter. However, additional effects that lower the gas temperature can substantially weaken the expected constraints on exotic energy injection, whereas additional radiation backgrounds can conceal the effect of an increased gas temperature in measurements of the 21-cm hyperfine transition of neutral hydrogen. Motivated in part by recent claims of a detection of 21-cm absorption from a redshift of 17 by the EDGES experiment, we derive the constraints on dark matter annihilation and decay that can be placed in the presence of extra radiation backgrounds or effects that modify the gas temperature, such as dark matter-baryon scattering and early baryon-photon decoupling. We find that if the EDGES observation is confirmed, then constraints on light dark matter decaying or annihilating to electrons will in most scenarios be stronger than existing state-of-the-art limits from the cosmic microwave background, potentially by several orders of magnitude. More generally, our results allow mapping any future measurement of the global 21-cm signal into constraints on dark matter annihilation and decay, within the broad range of scenarios we consider.

    ↳ astro-ph.COhep-phPRD(2018)·155 citations
31. 31*

    Non-minimally Coupled Pseudoscalar Inflaton

    Juan P. Beltrán Almeida🇨🇴 · Nicolás Bernal🇨🇴

    We consider a scenario in which the inflaton $\varphi$ is a pseudoscalar field non-minimally coupled to gravity through a term of the form $\mathcal{X}R{\varphi }^2$. The pseudoscalar is also coupled to a $U(1)$ gauge field (or an ensemble of $\mathcal{N}$ gauge fields) through an axial coupling of the form $\varphi F\tilde{F}$. After M. M. Anber and L. Sorbo, Phys. Rev. D 81, 043534 (2010), Ref. [1], it is well known that this axial coupling leads to a production of gauge particles which acts as a friction term in the dynamics of the inflaton, producing a slow-roll regime even in presence of a steep potential. A remarkable result in this scenario, is that the spectrum of the chiral gravitational waves sourced by the scalar-gauge field interplay can be enhanced due to the non-minimal coupling with gravity, leading to measurable signatures, while maintaining agreement with current observational constraints on $n_s$ and $r$. The inclusion of non-minimal coupling could be helpful to alleviate tensions with non-Gaussianity bounds in models including axial couplings.

    ↳ astro-ph.COgr-qchep-phPRD(2018)·9 citations
32. 32*

    Unifying Dark Matter and Dark Energy with non-Canonical Scalars

    Swagat S. Mishra🇮🇳 · Varun Sahni🇮🇳

    Non-canonical scalar fields with the Lagrangian $\mathcal{L}=X^{\alpha }-V(\varphi )$, possess the attractive property that the speed of sound, $c_s^2=(2\alpha -1{)}^{-1}$, can be exceedingly small for large values of $\alpha$. This allows a non-canonical field to cluster and behave like warm/cold dark matter on small scales. We demonstrate that simple potentials including $V=V_0{\coth }^2\varphi$ and a Starobinsky-type potential can unify dark matter and dark energy. Cascading dark energy, in which the potential cascades to lower values in a series of discrete steps, can also work as a unified model. In all of these models the kinetic term $X^{\alpha }$ plays the role of dark matter, while the potential term $V(\varphi )$ plays the role of dark energy.

    ↳ gr-qcastro-ph.COhep-phhep-thEPJC(2021)·16 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.